Film speed testing

[Mark MacKenzie]

No, aperture is a mathematical constant. It is the ratio between the focal length and the diameter of the lens or opening. It is as reliable as any other variable. That said, sure some manufacturers may mis-mark the aperture but I would think its very rare. The film testing is to match your darkroom variables to whatever paper you use to whatever enlarger you use to whatever timer you use, ph of water and so on, etc.

f/8 on a 48" telescope mirror is the same as f/8 on a 50mm Minolta lens. It is a mathematical certainty. You can argue transmission factors but they are miniscule.

For me the beauty of film testing is the expansion or contraction of contrast. This is of paramount importance in the darkroom, perhaps not in Photoshop.


Reading above... I think the danger in anything is not keeping proper prospective as far as to what extent do you need to exert yourself. Sure, you may have a lens that shoots 1/25 and the other shoots 1/27th of a second, but we are just getting into the ballpark, we don't need to know the speed of the fastball unless we are gluttons for punishment.

Seriously, if you are doing scientific studies of light output of the star Sirius, then you should be concerned with fractions of degrees on your thermometer or millisecond differences or how accurate the aperture markings are. For me, I am just wanting to get a good range of light on a piece of paper, sometimes more, sometimes less, but always in my control. I don't want accidental success. I don't mind it, but I don't rely on it.

Read those Ansel books. Honestly, they will tell you all you could ever want to know to make fine photos.

Sorry, one more point. You have to standardize before you can ever know what you are doing. One film, one paper, one developer, etc. Once you know how, say, HC-110 works, then you can play with D-23 or Pyro. It gets easier that way. Its a far shorter path then trying this then that then this then that and wondering why your prints always look like grey fog.

Maybe I've opened my mouth. They say its better to be thought a fool than to open your mouth and remove all doubt...

[AJ Edmondson]

Bill Burk's advice is pretty sound and is worth executing because it is a good learning experience. I realize that we are all different and have different approaches/goals but, having been down about every path proposed over the last 50+ years using field and view cameras I can vouch for the frustration which comes from trying to control - to the nth degree - all of the variables of the photographic process! If you consider, beginning with the light meter, the method of metering, the shutter and diaphragm, the lens transmission factor, the film speed, the amount of lens flare/internal flare, thermometer, agitation.... you get the picture (no pun intended). The list of variables is phenomenal and it is easy to become so enamored of "the perfect negative" that the pure joy of photography is lost amidst the noise. I recall being at some seminar back when Phil Davis first produced the "Beyond the Zone System" series that a fairly well-respected photographer was queried (with regard to the methodology) and his reply was pretty astounding... "get the book, work with it until you understand the approach, and then forget about it" ... (shock).
The truth is - again, my opinion only, the photographic process is pretty tolerant of errors. I also recall being at a seminar with John Sexton and seeing "straight prints" from Ansel Adams "Clearing Winter Storm" (the negative appeared almost bulletproof) and realizing that the art of printing, which is far more controllable, was the better approach for me. At that point I decided to test my equipment only to the extent necessary to prevent gross errors... an annual check of shutter speeds, light meter validation, thermometers. I suppose the approach should be governed by the objective - sensitometry or photography. This is not meant to be derisive of those who choose to pursue the alternatives. (I had to really fight the "test-it-to-death" approach because my profession was metrology conducted under what was then the National Bureau of Standards - now the National Institute of Standards and Technology.)

[Bill Burk]

But thinking of it logically...
The way I see it, the film is a constant, regardless of what camera or lens...
Shutter speed is something that you can test to see what you are actually getting...so that becomes a pretty reliable factor.

The unknown, untested, take on faith factor is the aperture.

Logic would dictate that it is the aperture that has variables in it. f/8 on this lens lets in more light than f/8 on that lens, therefore I have to change the ISO to compensate.
I do not see any other way to compensate except by varying the ISO, but aperture is where I see the problem originating.

People like Stephen Benskin say it's always best to break down to individual variables.

If you were striving for a complete device-independent system, you would separate everything:

-Film speed: test with sensitometer and note the effective film speed for your development technique and quality demands
-Shutter speed: test with shutter tester and mark the shutter with a cheat sheet with the real times
-Aperture: test on optical bench and mark T-Stops (transmission stops) on your lenses like they do for movie cameras.
-Light meter: I've heard of all our devices, the light meter is the most accurate (there is a K factor, which has its own urban legend qualities, the proof is ugly but seems correct to me).
-Flare: Beyond the Zone System describes a test for flare, I like to lay down a costume "top hat" in the picture.

Classic Zone System testing includes all these variables and bunches them together so the test is only valid for your setup at the shutter speed you picked...

I don't say I know how bad each of these variables is, but I can start to name them.

For discussion purposes, I don't think f/stops are that bad. Here's my logic:

Motion picture camera operators need to have very accurate lens markings. They get their lenses bench tested and rated for transmission... T-stops. Still Film Photographers have de-facto accepted f/stops as "good enough". I believe the reason is purely cost - but I wouldn't rule out brainwashing.

So I don't think aperture is that big of a variable. You can send your lenses off to S.K. Grimes and they can engrave an accurate scale for you. Never mind, you say? That's OK.

I hate to read forum posts when people say "don't worry about it, it doesn't matter". So I hope that's not how I'm coming across. I mean... of course it matters and it is important to get your head around it. I am happiest when I use my understanding of a concept to solve a problem. But I also am happy to put my long discussions to rest when I am out taking pictures and shoot at f/4.7 even though if the meter and my calculations indicate f/4.

I think you could test aperture by shooting a test series with Flash! Setup a gray card, terrycloth towel, etc. Then with flash on Manual, shoot at all the different apertures. Measure the result with a densitometer and graph next to a sensitometry test. The difference on the Log-E axis will tell you the real T-stop!

[Bill Burk]

I recall being at some seminar back when Phil Davis first produced the "Beyond the Zone System" series that a fairly well-respected photographer was queried (with regard to the methodology) and his reply was pretty astounding... "get the book, work with it until you understand the approach, and then forget about it" ... (shock)

Thanks AJ Edmondson,

Exactly what I was trying to say... The understanding you gain is what makes the Zone System seminars and books and threads so valuable. Once you internalize it, you are free. And freedom is precious.

[Lenny Eiger]

I think this is very simple. Sure there are a lot of variables, but the differences between lenses isn't going to make that much of an effect - not a whole stop for instance. In addition, this would only affect the shadows. The first thing you would want to do is look at a negative that was perfect.... the one that printed itself. You had to do no burning and dodging and the print came out exactly the way you want it. The very black part of the shadows should be almost clear and the highlights shouldn't blow out. If you don't have an example of this, find someone who does and look hard at their negative. I used to do all the densitometry, taught classes in it at colleges, and now I just look and see if I like what's on the light table. Then I see if it prints... It's only rocket science if you are doing science, comparing two films equally for a review, etc. Making a great negative is about getting the print you want, not necessarily what anyone else wants.

I think Bill Burk's offer is quite generous, he can obviously help, and you should call him on the phone and arrange it. There is nothing like being shown "the ropes" even if you ultimately decide to "improve" on the process for your own purposes.


Lenny

[Chuck P.]

I'm afraid your worst fears are about to materialize. My understanding is that the combination camera, lens, film is what determines the appropriate film speed. So, depending on how many lenses you use on a given camera, and hoping--for your sake--that you only use one kind of film, that's how many combinations you have of film speed. So, one camera, three lenses, and assuming just one kind of film, will have up to three different results.

Luckily for me, for my 4x5, I only have one lens and one kind of film I use. So my testing becomes very easy.

If one believes that this guy knew what he was talking about, one would know that he abslolutley did not recommend what you are suggesting here to the OP.

[Doremus Scudder]

Okay, I'm trying to do a film speed testing, ... Can someone give me the easy version of the film speed test? Thanks.

I think we are making things a bit too difficult here. The OP is a beginner and wanted to find a personal film speed. He is daunted by working in fractions of a stop.

Plus, finding a personal E.I. that you can use and get good results from is not all that difficult. Sure, there is a whole lot of science and lots of variables in lenses, cameras, flare, etc. that we can figure in, but I never worried about that when I was starting out.

I recommend to the OP to do a simple test with his grey card, the camera and lens he uses most often and the film he wants to test. This assumes a fairly modern, correctly working shutter. Testing it would be nice, but if 1 second and 1/2 second sound good, that should be fine.

Set the film speed on the meter to half of the box speed of the film (one stop overexposure; e.g., if you are testing 400 speed film, set the meter to 200). Meter the card and place it in Zone 1. Pull the darkslide halfway and shoot (use a slow shutter speed, they are more accurate). Do the same a 1/3 stop slower than box speed (i.e., the next film speed slower than box speed, for 400 speed film that would be 320).

Develop these negatives and read them with the densitometer. Find the Zone I density that is the closest to 0.01 above FB+F without being under that value. Use that for starters. If it looks like the intermediate speed (the one that wasn't tested) is better, e.g., if the 1/3-stop under was just a bit under 0.01 above FB+F, and the one-stop over neg is way over, then use that instead.

Or, you can ditch the densitometer completely and make proper proofs. Find minimum time for maximum black on your printing paper for the clear area of the neg. Print your negs at that time and lighting. Find the strip that just starts to show grey. That's your Zone I and your film speed.

Then do a test for N development and expansions and contractions if you like and go out and shoot. Make adjustments to your system based on your shooting in the field.

That's more than enough to get started and get good results.

Best,

Doremus

[Bill Burk]

I think we are making things a bit too difficult here. The OP is a beginner and wanted to find a personal film speed.

Doremus,

You gave the simplest film test idea, and I endorse it.

As to the other answers being too difficult, sure I went off the deep end. But I believe OP is about to embark on a journey searching for a deeper understanding (so he can soak in the gritty details)... He's asked for books... This is the kind of hunger for knowledge that gets accelerated faster than any learning in schools can deliver (I think I just read an Edward Abbey passage to that effect).

I would say the high level view is... For black and white it's all about "expose for the shadows, develop for the highlights". For color (OP has indicated interest in color), since there are three layers of carefully balanced film, you cannot control contrast by development because it will throw off the balance, so the film gets developed "a standard amount."

I don't know color that well so correct me if I'm wrong: Color balance can be compensated easily with filters. Contrast control is done with masking if necessary. If possible... deal with contrast in advance by altering the light ratio when shooting.

[macandal]

Thanks for all the suggestions folks. I have a question. This may be totally irrelevant, but here goes, why when doing the film speed test, you are asked to go up/down a half stop or a third stop? Why not a full stop? Is there something about half and third stops that I'm not seeing? Thanks.

[DennisD]

Mario,
1/2 or 1/3 stop increments should allow you to hone in on (or come very close to) a densitometer reading of 0.1 above FB + F as described by Doremus. This is better than trying to interpolate. Going in one stop increments might be ok if you're lucky but could easily result in your making an estimate that will lead to determination of a film speed that's not as accurate as you might otherwise achieve.

You really want to the correlate the 0.1 above FB + F densitometer reading as closely as possible with as possible with specific readings - not estimates.